In the microelectronics industry, as well as in other industries involving construction of microscopic structures, e.g., micromachines and magnetoresistive heads, there is a desire to further reduce the size of structural features. In the microelectronics industry in particular, while the size of microelectronic devices is being reduced, a greater amount of circuitry for a given chip size is being required.
Effective lithographic techniques are essential to reducing the size of structural features. Lithography impacts the manufacture of microscopic structures, not only in terms of directly imaging patterns on the desired substrate, but also in terms of making masks typically used in such imaging.
Most lithographic processes use an antireflective coating (ARC) to minimize the reflectivity between an imaging layer, such as a radiation-sensitive resist material layer, and an underlayer to enhance resolution. However, these ARC materials impart poor etch selectivity to the imaging layer due to the layers' similar elemental compositions. Therefore, during etching of the ARC after patterning, a lot of the imaging layer is also consumed, which may have been needed for additional patterning during subsequent etch steps.
In addition, for some lithographic techniques, the radiation-sensitive resist material employed does not provide resistance to subsequent etching steps sufficient enough to enable effective transfer of the desired pattern to the layer underlying the radiation-sensitive resist material. In many instances, a hardmask layer is used for example, where an ultrathin radiation-sensitive resist material is used, where the underlying layer to be etched is thick, where a substantial etching depth is required, where it is desirable to use certain etchants for a given underlying layer, or any combination of the above. The hardmask layer serves as an intermediate layer between the patterned radiation-sensitive resist material and the underlying layer to be patterned. The hardmask layer receives the pattern from the patterned radiation-sensitive resist material layer and transfers the pattern to the underlying layer. The hardmask layer should be able to withstand the etching processes required to transfer the pattern.
While many materials useful as ARC compositions are known, there is a need for improved ARC compositions with high etch selectivity to the radiation-sensitive resist material, to the hardmask layer and to the underlying layer. Further, many of the known ARCs are difficult to apply to the substrate, e.g., applying these ARCs may require the use of chemical vapor deposition, physical vapor deposition, special solvents, high temperature baking or any combination of the above.
Thus, it would be desirable to be able to perform lithographic techniques with high etch selectivity yet sufficient resistance to multiple etchings. Such lithographic techniques would enable production of highly detailed semiconductor devices.